Adherence to ART, fundamental to treatment success, has been poorly studied in India. Caregivers of children attending HIV clinics in southern India were interviewed using structured questionnaires. Adherence was assessed using a visual analogue scale representing past-month adherence and treatment interruptions >48 h during the past 3 months. Clinical features, correlates of adherence and HIV-1 viral-load were documented. Based on caregiver reports, 90.9 % of the children were optimally adherent. In multivariable analysis, experiencing ART-related adverse effects was significantly associated with suboptimal adherence (p = 0.01). The proportion of children who experienced virological failure was 16.5 %. Virological failure was not linked to suboptimal adherence. Factors influencing virological failure included running out of medications (p = 0.002) and the child refusing to take medications (p = 0.01). Inclusion of drugs with better safety profiles and improved access to care could further enhance outcomes.